The present invention generally relates to document feeders. More particularly, the present invention relates to a method and system for generating a predetermined feed spacing between a first document and a second document in a document feeder.
Document processing is a function performed by a wide variety of devices such as check processors, copiers, fax machines, printers, automated teller machines, and scanners. In all of these devices, typically one or more feed wheels will retrieve documents from a document stack and transport them along a given feed path. Often, a separator or retarder will be positioned on the opposite side of the document in order to ensure that the documents are retrieved one-by-one from the document stack.
One or more transport wheels are typically disposed farther along the feed path in order to transport the document to the desired location. While the above-described feeder wheel/separator mechanism is often effective in preventing feed overlap, sometimes parameters such as humidity, document weight, and document texture continue to cause feed overlap. To further address feed overlap, conventional document feeders typically drive the transport wheel at a higher speed than the feeder wheel. The speed differential is intended to cause a space to be developed between the two documents. This space is normally required for actuating pocket selector gates, advancing microfilm, or processing other information. Thus, normally the separator holds back the second document until the trailing edge of the first document leaves the feeder nip. Occasionally, however, it has been observed that the second document will still feed too soon resulting in overlap of consecutive documents. Depending on the amount of overlap, the higher speed of the transport wheels may still be able to separate these documents. The resulting space, however, maybe too small to allow satisfactory operation of pocket selector gates, for example. It is therefore desirable to provide a mechanism for eliminating overlap between subsequent documents in a document feeder.
Another concern relates to the insertion of a constant feed spacing between the documents. In this regard, it is important to note that the above-described feeder wheel/transport wheel speed differential results in feed spacings that are proportional to the length of the second document. This increased space for longer documents is unnecessary and decreases throughput. It is therefore also desirable to provide a control system capable of inserting a predetermined feed spacing between documents regardless of document length.
The above and other objectives are provided by a method for generating a predetermined feed spacing between a first document and a second document in accordance with the principles of the present invention. The method includes the steps of determining an adjustment time period, and reducing a feed wheel speed to an adjustment speed. The feed wheel transports the documents between a document stack and a transport wheel. The method further provides for increasing the feed wheel speed after the adjustment time period has expired, such that the trailing edge of the first document and the leading edge of the second document have the predetermined feed spacing. Reducing, the feed wheel speed for a variable adjustment time period provides an enhanced approach to constant feed spacing unachievable through conventional approaches.
The present invention further provides a method for determining an adjustment time period. The method includes the step of determining a desired change in feed spacing between a first document and a second document based on an initial feed spacing and a predetermined feed spacing. A wheel speed difference is also determined based on a transport wheel speed and an adjustment speed of a feed wheel, where the feed wheel transports the documents between a document stack and the transport wheel. The method further provides for determining the adjustment time period based on the desired change in feed spacing and the wheel speed difference.
Further in accordance with the present invention, a document feed control system includes a feed wheel controller and an adjustment module. The feed wheel controller reduces a feed wheel speed to an adjustment speed, where the feed wheel transports a first document and a second document between a document stack and a transport wheel. The feed wheel controller increases the feed wheel speed after an adjustment time period has expired such that a trailing edge of the first document and a leading edge of the second document have a predetermined feed spacing. The adjustment module determines the adjustment time period.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.